Type of received value [big number] is not suitable for value type [Numeric (float)] is the error received when a SNMP value gets multiplied by a big number.
An example could be 1073741824 (1024*1024*1024) when using the "Use custom multiplier" field, it might fail if the calculation result is too big.

Multiplying 315.2 with 1073741824 should result in 338443422924.8, but in Zabbix it results in 338443422924.799988.

If the number is even bigger, say 229204.4 times 1073741824 it should result in 246106350524825.6, but the item instead gets unsupported. Maybe because an additional five digits gets added as decimals like in the example above, pushing the number above the some size limit ?

These examples are SNMP values received as gigabyte sizes, on free and total disk space from a monitored storage unit. The plan is then to convert them into byte sizes to use Zabbix post processing by specifying "B" in the "Units" field on the template item.